what size resistor would i need?

Discussion in 'Electrical' started by zalmaad, Dec 14, 2014.

  1. zalmaad

    zalmaad New Member

    hi

    please
    [h=1]what size resistor would i need ?
    [/h]
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  2. Nate888

    Nate888 Member

    trick question - you really need 4x of the LED unit. brighter and the amps match up as long as you connect them in.. um, either series or parallel, but not the other? I'm a hella crappy electrician, but that's my 2ยข worth

    [edit: I'd had a few drinks; pardon the bad advice, & thank jaguar for providing the correct answer below]
     
    Last edited: Dec 7, 2016
  3. jaguar

    jaguar Well-Known Member

    no resistor is needed since the LED can handle 12 volts
     
  4. CrazyDan

    CrazyDan Active Member

    The battery's mAh tells you how many amp hours the battery can hold, in this case 3.6 amp hours. With that 900 mA LED you should get 4 hours of runtime on full blast.
     
  5. Frankenstein

    Frankenstein Well-Known Member

    I'm in agreement with jag, my headlamp uses the same basic Cree led chip. They all should handle 12 volts no problem.

    If it was one of their smaller chips that handle 4-6 volts then you'd need the resistor.

    Now I would suggest double checking your battery type. If you pick a standard starting battery you'll kill it in a couple months unless you really keep on top of its charge, a starter battery is not meant to be left in a discharged state. You want a deep cycle battery (seen on backup power sources universally) which can be charged down pretty far and no harm comes of it. Should you leave the lights on for a week and come back from vacation to a dead battery you'll at least still have a working battery once you charge it. A cranking battery could suffer greatly from the same treatment and simply be damaged beyond any good use.
     
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